The timed text track feature provides useful capabilities in HTML that do not need to be bound to one specific format. For example, IE10 PP4 implements a subset of both the W3C Recommendation TTML and the experimental community group driven format WebVTT. Both are equally appropriate formats and IE10 PP4 would be interoperable with a user agent implementing a similar profile of TTML.

WebVTT could also feasibly be used as a timed text format independently from HTML5. There is therefore no reason to tie the two formats together with a mutual dependency.